The present invention relates to a self aligning stuffing box for pumpjacks.
The pumping action of a beam pump, commonly known as a xe2x80x9cpumpjackxe2x80x9d, moves a polished rod in a reciprocating motion. The polished rod extends through an axial bore of a stuffing box. The stuffing box contains packing which forms a seal against the polished rod. If the polished rod is not axially aligned with the axial bore of the stuffing box, lateral pressure is exerted upon the stuffing box by the polished rod. This lateral pressure leads to wear and premature failure of both the packing and the polished rod.
In order to address problems of wear due to improper alignment, stuffing boxes have been developed that are self aligning. U.S. Pat. No. 3,887,196 (Renfrow) discloses a self aligning stuffing box in which a first body provides a socket and a second body provides a ball. The ball and socket engagement enables limited universal movement between the first body and the second body.
The present invention relates to an alternative configuration of self aligning stuffing box for pumpjacks.
According to the present invention there is provided a self aligning stuffing box for pumpjacks which includes a first tubular body having a first end, a second end, an exterior surface and an interior surface defining an interior bore. The interior surface at the second end has internal stops. A second tubular body is provided having a first end, a second end, an exterior surface and an interior surface defining an interior bore. The first end has a concave contact surface. The second tubular body is telescopically received within the first tubular body with the first end of the second tubular body precluded from withdrawal from the second end of the first tubular body by the internal stops. An annular body is disposed within the interior bore of the first tubular body. The annular body has a first end and a second end. The second end has a convex contact surface which engages the concave contact surface of the second tubular body. A third tubular body is provided having a first end, a second end, an exterior surface, and an interior surface defining an interior bore. The second end of the third tubular body is telescopically received in the first tubular body and exerts a compressive force upon the annular body to maintain the convex contact surface of the annular body engaged with the concave contact surface of the second tubular body. At least one tubular packing housing is provided having a first end, a second end, an exterior surface and an interior surface defining a packing chamber which is adapted to receive packing. Either the first end or the second end of the tubular packing housing is coupled to either the second end of the second tubular member or the first end of the third tubular member.
Although beneficial results may be obtained through the use of the self aligning stuffing box, as described above, even more beneficial results may be obtained when additional features are incorporated into the stuffing box. For example a fluid responsive flapper valve can be pivotally mounted within the interior bore of the stuffing box, such that upon removal of a polished rod from the interior bore, the flapper valve closes the interior bore-in response to fluid pressure.